This [revised] R21 application seeks two years of support to develop state-of-the-science methodologies to address four important gaps in existing research with homeless women: 1) capture the diversity of circumstances among a fluid and hard-to-access population;2) increase our understanding of mental and substance use disorders (particularly personality disorders) across the diversity of homeless women;3) improve our understanding trajectories to homelessness through development of an innovative event history calendar approach;and 4) advance knowledge of homeless women's health and HIV-risk by circumstance and trajectories to homelessness. This research will provide measurement development and preliminary studies for a multi-state longitudinal R01 designed to advance our understanding of mental and substance use disorders among homeless women, their movement into and out of homelessness, the consequences of homelessness for women and minor children in their custody, and women's health, HIV-risk, and HIV testing behaviors. The planned longitudinal research will focus on a growing but poorly understood population of the nation's most vulnerable women. The specific aims of this R21 developmental application are to 1) develop and pilot a sampling plan that will better reflect the diversity of homeless women;2) develop and pilot an innovative events history calendar for use with homeless women;3) program and pilot Axis 1 (UM-CIDI) and Axis II (DIPD-IV) diagnostic interview schedules for computer-assisted personal interviews with homeless women;4) develop and program women's health and HIV-risk measures;and 5) pilot the measures with 200 homeless women in two Midwestern cities. PUBLIC HEALTH RELEVANCE: This [revised] R21 developmental application will set the stage for the first multi-state longitudinal diagnostic study of homeless women. It builds on more than a decade of work with hard to access homeless populations and a prior three-year longitudinal diagnostic study of homeless adolescents. This application will fund the development of innovative measures and sampling techniques specifically for this understudied population and for the piloting of measures with a sample of 200 homeless women in two Midwestern cities.